UIC comfort tests - VTI

Each element may provoke a potential discomfort:Circular curves add horizontal lateral acceleration due to centrifugal forces. Thislateral acceleration is partly compensated by the cant of the track (see later). Theremaining lateral acceleration at the track level is commonly described as theNon-Compensated lateral Acceleration (NCA). The cant of the track not onlycompensates for lateral acceleration but also introduces vertical supplementaryweight as the vertical component of the centrifugal force. Tilting coaches are ableto reduce the lateral acceleration percieved by the passenger further, so that only afraction of the original acceleration remains. In this report, we will indicate thispart as the remaining lateral acceleration (RLA) (i.e. the mean laterial accelerationperceived by the passengers).Curve transitions add "roll speed" and "jerk" as commonly used parameters fordescribing discomfort. But there is also a vertical speed because of the changingangle of the coach. Moreover the remaining lateral acceleration and the verticalacceleration change from zero to their equilibrium values in the circular curves.The intersection points of the curve transition with other elements add "rollacceleration" and "vertical acceleration" due to sudden changes in cant andpossible tilting action.Because of the importance of transition curves in relation to comfort, it iscommon to treat different situations separately because of their distinct influenceon coaches and passengers.The following types of transition curve can be distinguished, describing thephenomena by the angle of both bogies and the angle of the coach as input,together with a hypothetical behaviour of the coach as lateral acceleration in carbody plane:SIMPLETRANSITION CURVERed: bogie 1 angleBlue: bogie 2 angleGreen: car body angleFuchia: Lateral acc. incar body20 VTI notat 56A-2003